Cfd Meshing Caea
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Transcript of Cfd Meshing Caea
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CFD Meshing withor enc
March 14, 2013
2013 CAE Associates
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Agenda
Efficient Meshing for CFD
Live Demonstration
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ANSYS Workbench Mesh Methods
Hexahedral Methods: weep Multizone Hex Dominant CutCell (Fluent Only) Hex Cell
Tetrahedron Methods: Patch Conforming Patch Independent
Tet Cell
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Mesh Methods
Sweep requires topologically consistent source and target faces (same number
of vertices per face with a smooth path from the source to the target). ,
it is free meshed with tetrahedral elements. Specify manual source (and target faces) when:
There exists more than one possible sweep direction You want to sweep mesh a thin solid with a single element through the thickness You want to inflate the mesh near the surface of the geometry
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Mesh Methods
The number of elements in the sweep direction along with the bias settings are
also set in the sweep details.
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Mesh Methods
ICEM Advanced Meshing Module) that internally segments bodies intotopologically consistent pieces.
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Mesh Methods
Two algorithms exist for tetrahedral meshing
=
The mesh must conform to the boundaries of thefaces, yielding a very fine mesh in regions withsmall faces.
e au me o
Algorithm = Patch Independent:
boundaries of the faces. This is useful when there are many small faces
which would normally produce a very fine mesh.
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Mesh Methods
Tetrahedral Mesh Example: Patch conformin mesh: 28,050 elements Geometry with very small
faces relative to the overallgeometry.
Patch independent mesh: 11,579 elements
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Efficient CFD Meshing
Why do I want a hex mesh? Elements generally come in a few basic shapes:
Hexahedron (hexas, bricks) Pentahedron (wedges, prisms) Tetrahedron
Pyramids
Hexahedrons can fill a given volume more efficiently than other mesh shapes It takes approximately 5-6 tetrahedrons to fill 1 hexahedron.
Hex Pyramid TetWedge
Fewer elements lead to faster solution times Hexahedron meshes are generally more uniform
Easier control of the element distribution
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exa e rons can e more accurate w en a gne w t t e ow recton Not always possible to align the mesh with the flow direction
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How Do I Get a Hex Mesh?
Hex meshes always take more man-time than tetrahedral meshes. Hex meshes are usually created using one or more of the following
Slice and dice the solid geometry to create 6-faced volumes, each face having 3 or4 boundary curves. Create a 2D mesh of quadrilaterals and sweep or extrude the 2D mesh to create 3D
exas. yp ca opera ons nc u e: Revolve the mesh about an axis. Sweep the mesh along one or more curves. Sweep a surface mesh from one face of a volume to a topologically similar face on the
opposite face of a volume.
Hex meshes can also be created with advanced meshing methods.
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How Do I Get a Hex Mesh?
. ,an all-hex mesh can be created with some effort by the user.
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How Do I Get a Brick Mesh?
DesignModeler and forming theresulting bodies into a part, wecan et a collection of swee able
bodies.
capture the inlet pipe curvatureand with 5 inflation layers alongthe walls.
The resulting mesh contains, .
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How Do I Get a Hex Mesh?
tetrahedron mesh resulting fromthe unaltered geometry is shownto the ri ht.
Again, the mesh is generated to
and with 5 inflation layers alongthe walls. The part is meshedwith ver little effort.
The resulting mesh contains,
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Combining Methods
bodies are formed into a part!
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Selective Meshing
. Named selections are created to control the order of meshing (not sent to the
solver) Note: The automatic method is still used for arts without a s ecified mesh
method.
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Summary
CFD mesh
x
Ease of use of ANSYS Workbench makes generating high fidelity meshesa simple process
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